Functional element having electrically controllable optical properties

ABSTRACT

An improved functional element having electrically controllable optical properties includes a stack sequence formed of a first carrier film, a first surface electrode, an active layer, a second surface electrode, and a second carrier film, wherein the second carrier film is folded around the edge of the first carrier film at least at one side edge and seals an exit surface of the active layer at the side edge.

The invention relates to a functional element having electricallycontrollable optical properties and in particular a windshield with anelectrically controllable sun visor, a method for producing such afunctional element, as well as a composite pane having a functionalelement.

In the vehicle sector and in the construction sector, composite paneswith electrically controllable functional elements are often used as sunscreens or as privacy screens.

Thus, for example, windshields are known in which a sun visor isintegrated in the form of a functional element having electricallycontrollable optical properties. In particular, the transmittance orscattering properties of electromagnetic radiation in the visible rangeare electrically controllable. The functional elements are usuallyfilmlike and are laminated into or glued onto a composite pane. In thecase of windshields, the driver can control the transmittance behaviorof the pane itself relative to sunlight. Thus, a conventional mechanicalsun visor can be dispensed with. As a result, the weight of the vehiclecan be reduced and space gained in the roof region. In addition, theelectrical control of the sun visor is more convenient than the manualfolding down of the mechanical sun visor.

Windshields with such electrically controllable sun visors are, forexample, known from WO 2014/086555 A1, WO 2017/157626 A1, DE102013001334 A1, DE 102005049081 B3, DE 102005007427 A1, and DE102007027296 A1.

Typical electrically controllable functional elements containelectrochromic layer structures or suspended particle device (SPD)films. Further possible functional elements for realizing anelectrically controllable sun screen are so-called PDLC functionalelements (polymer dispersed liquid crystal). Their active layer containsliquid crystals that are embedded in a polymer matrix. When no voltageis applied, the liquid crystals are randomly oriented, resulting instrong scattering of the light passing through the active layer. When avoltage is applied on the surface electrodes, the liquid crystals alignthemselves in a common direction and the transmittance of light throughthe active layer is increased. The PDLC functional element acts less byreducing total transmittance, but, instead, by increasing scattering toensure protection against dazzling. Such functional elements are, forexample, known from DE 202018102520 U1.

Prior art, laminated functional elements and, in particular, PDLCfunctional elements often present, in the edge region, undesirable agingphenomena, such as brightening and changes in shading, as is known, forexample, from WO 2007/122429 A1.

The object of the present invention is, consequently, to provide animproved functional element having electrically controllable opticalproperties that is improved, in particular, with regard to its agingresistance.

The object of the present invention is accomplished by a functionalelement in accordance with the independent claim 1. Preferredembodiments emerge from the dependent claims.

Further aspects of the invention include improved composite panes havingfunctional elements according to the invention as well as methods forproducing the functional element, methods for producing a compositepane, and use thereof.

A functional element having electrically controllable optical propertiescomprises at least a stack sequence formed of

-   -   a first carrier film,    -   a first surface electrode,    -   an active layer,    -   a second surface electrode, and    -   and a second carrier film,

wherein the second carrier film is folded around the first carrier filmat least at one side edge.

In an advantageous embodiment of the functional element according to theinvention, the second carrier film seals an exit surface of the activelayer at the respective side edge.

The first surface electrode is arranged on the inward surface of thefirst carrier film and preferably bonded directly thereto. The secondsurface electrode is arranged on the inward surface of the secondcarrier film and preferably bonded directly thereto.

As a result of folding the second carrier film around the side edge ofthe first carrier film, the inward surface of the second carrier film isarranged, in the folded region, in the immediate proximity of theoutward surface of the first carrier film.

In an advantageous development of the functional element according tothe invention, the second carrier film has an overhang beyond the firstcarrier film, i.e., the second carrier film has an overhanging regionwith the width u. In other words: the second carrier film is dimensionedwider in this region.

The terms “overhang” or “to overhang” mean, as generally commonly used:to protrude beyond something in a lateral (horizontal) direction. Inthis case, the second carrier film protrudes in the plane of thefunctional element beyond the first carrier film. Here, “lateral” meansas generally commonly used: to the side or sideways. To simplify thedescription, the entire region around which the second carrier film islonger that the first carrier film is referred to as the “overhangingregion”, even when the overhanging region is routed out of the lateralplane and folded around the side edge of the first carrier film. Thefolding can be carried out manually or automated by machine, forexample, by a robot.

The overhanging region advantageously has a width u of at least 4 mm,preferably of at least 6 mm, and particularly preferably of at least 8mm.

The overhanging region preferably has a maximum width u of 50 mm,preferably of 20 mm, and particularly preferably of 10 mm. Particularlyadvantageous is an overhanging region with a width u of 0.5 mm to 50 mm.

Alternatively, the overhanging region u of the second carrier film canbe wider than the entire first carrier film such that the folded-aroundregion of the second carrier film completely covers the outward surfaceof the first carrier film and preferably protrudes beyond the side edgeopposite the folding or, particularly preferably, is folded around itagain.

In an advantageous development of the functional element according tothe invention, the overhanging and folded-around region is materiallyand/or form-fittingly bonded to an edge region of the first carrierfilm, preferably fused and/or glued.

In an advantageous development of the functional element according tothe invention, the width w of the region folded around and bonded to theedge region of the first carrier film is roughly equal to the width ofthe overhang u minus the sum of the thickness of the first carrier film,the thickness of the first surface electrode, the thickness of theactive layer, and the thickness of the second surface electrode. As aresult, the second carrier film rests, in the overhanging region, closeto the exit surface of the active layer and the side edge of the firstcarrier film and, thus, seals the exit surface particularly well and,ideally, hermetically.

Of course, the functional element can have a folded-around sealaccording to the invention at at least one side edge, preferably at two,three, four, or all side edges. It is irrelevant for the seal whetheronly the second carrier film has an overhanging region at one or aplurality of the side edges or whether alternatively even at least onefirst carrier film has an overhanging region that is folded around thesecond carrier film.

A composite pane according to the invention comprises at least:

-   -   a stack sequence formed of an outer pane, a first intermediate        layer, a second intermediate layer, and an inner pane, wherein        the intermediate layers include, in each case, at least one        thermoplastic polymer film with at least one plasticizer, and    -   a functional element according to the invention having        electrically controllable optical properties is arranged between        the first intermediate layer and the second intermediate layer        at least in sections.

The composite pane can, for example, be the windshield or the roof panelof a vehicle or another vehicle glazing, for example, a separating panein a vehicle, preferably in a rail vehicle or a bus. Alternatively, thecomposite pane can be an architectural glazing, for example, in anexternal facade of a building or a separating pane in the interior of abuilding.

The terms “outer pane” and “inner pane” arbitrarily describe twodifferent panes. In particular, the outer pane can be referred to as “afirst pane” and the inner pane as “a second pane”.

When the composite pane is provided, in a window opening of a vehicle orof a building, to separate an interior from the external environment,“inner pane” refers, in the context of the invention, to the pane(second pane) facing the interior (vehicle interior). “Outer pane”refers to the pane (first pane) facing the external environment. Theinvention is, however, not restricted to this.

The functional element can also be arranged on both sides in thecomposite pane. In other words, either the first carrier film isarranged on the side of the functional element facing the outer pane oron the side of the functional element facing the inner pane.

The composite pane according to the invention includes a functionalelement having electrically controllable optical properties that isarranged, at least in sections, between a first intermediate layer and asecond intermediate layer. The first and second intermediate layercustomarily have the same dimensions as the outer pane and the innerpane. The functional element is preferably filmlike.

In an advantageous embodiment of a composite pane according to theinvention, the inward, folded-around regions of the second carrier filmand the outward edge of the first carrier film are bonded to oneanother, preferably pressed together (for example, by lamination in acomposite pane), glued, or welded (for example, by local heating). As aresult, a sufficient and secure diffusion barrier against plasticizersfrom the intermediate layer is produced and clouding of the edge regionof the functional element is reduced or prevented.

In another advantageous embodiment of a composite pane according to theinvention, the inward, folded-around regions of the second carrier filmand outward edge of the first carrier film are joined to one anotherover their entire surface and preferably glued, for example, by anadhesive, in particular by an acrylic-based adhesive, preferablyacrylate-based, and most particularly preferably an adhesive thatcontains more than 50% methyl methacrylate. This has the particularadvantage that slippage during assembly and during lamination is avoidedand the second carrier film film is firmly and fittingly joined to thefirst carrier film. As result, among other things, air inclusions areavoided and the optical quality of such functional elements andcomposite panes is particularly high.

The invention is based on the realization by the inventors that thediffusion of plasticizers out of the intermediate layers into theinterior of the functional element during aging results in a brighteningor a change in transmittance which impairs the through-vision andaesthetics of the composite pane. As a result of the sealing of the exitsurface of the active layer of the functional element with the carrierfilm, which impedes or prevents the diffusion of plasticizers out of theintermediate layer into the exit surface of the active layer, such agingphenomena are significantly reduced or completely prevented.

In an advantageous embodiment of a composite pane according to theinvention, the intermediate layer contains a polymer, preferably athermoplastic polymer.

In a particularly advantageous embodiment of a composite pane accordingto the invention, the intermediate layer contains at least 3 wt.-%,preferably at least 5 wt.-%, particularly preferably at least 20 wt.-%,even more preferably at least 30 wt.-%, and in particular at least 40wt.-% of a plasticizer. Preferably, the plasticizer contains or is madeof triethylene glycol-bis(2-ethyl hexanoate).

Plasticizers are chemicals that make plastics softer, more flexible,smoother, and/or more elastic. They shift the thermoelastic range ofplastics to lower temperatures such that the plastics have the desiredmore elastic properties in the range of the temperature of use. Otherpreferred plasticizers are carboxylic acid esters, in particularlow-volatility carboxylic acid esters, fats, oils, soft resins, andcamphor. Other plasticizers are preferably aliphatic diesters of tri- ortetraethylene glycol. Particularly preferably used as plasticizers are3G7, 3G8, or 4G7, where the first digit indicates the number of ethyleneglycol units and the last digit indicates the number of carbon atoms inthe carboxylic acid portion of the compound. Thus, 3G8 representstriethylene glycol bis(2-ethyl hexanoate), in other words, a compound ofthe formula C₄H₉CH(CH₂CH₃)CO(OCH₂CH₂)₃O₂CCH(CH₂CH₃)C₄H₉.

In another particularly advantageous embodiment of a composite paneaccording to the invention, the intermediate layer contains at least 60wt.-%, preferably at least 70 wt.-%, particularly preferably at least 90wt.-%, and in particular at least 97 wt.-% polyvinyl butyral.

The thickness of each intermediate layer is preferably from 0.2 mm to 2mm, particularly preferably from 0.3 mm to 1 mm, in particular from 0.3mm to 0.5 mm, for example, 0.38 mm.

The controllable functional element according to the invention includesan active layer between two surface electrodes. The active layer has thecontrollable optical properties that can be controlled via the voltageapplied to the surface electrodes. The surface electrodes and the activelayer are typically arranged substantially parallel to the surfaces ofthe functional element and in a composite pane substantially parallel tothe surfaces of the outer pane and the inner pane. The surfaceelectrodes are electrically connected to an external voltage source in amanner known per se. The electrical contacting is realized by means ofsuitable connecting cables, for example, foil conductors that areoptionally connected to the surface electrodes via so-called busbars,for example, strips of an electrically conductive material orelectrically conductive imprints.

The surface electrodes are preferably designed as transparent,electrically conductive layers. The surface electrodes preferablycontain at least a metal, a metal alloy, or a transparent conductiveoxide (TCO). The surface electrodes can contain, for example, silver,gold, copper, nickel, chromium, tungsten, indium tin oxide (ITO),gallium-doped or aluminum-doped zinc oxide, and/or fluorine-doped orantimony-doped tin oxide. The surface electrodes preferably have athickness of 10 nm to 2 μm, particularly preferably from 20 nm to 1 μm,most particularly preferably from 30 nm to 500 nm.

The functional element can have, besides the active layer and thesurface electrodes, other layers known per se, for example, barrierlayers, blocking layers, antireflection layers, IR reflection layers,protective layers, and/or smoothing layers.

The functional element is present as a multilayer film with two outercarrier films. In such a multilayer film, the surface electrodes and theactive layer are arranged between the two carrier films. Here, “outercarrier film” means that the carrier films form the two surfaces of themultilayer film. The functional element can thus be provided as alaminated film that can be processed advantageously. The functionalelement is advantageously protected by the carrier films against damage,in particular corrosion. The multilayer film contains, in the orderindicated, at least one first carrier film, one first surface electrode,one active layer, a second surface electrode, and a second carrier film.The carrier film carries, in particular, the surface electrodes andgives a liquid or soft active layer the necessary mechanical stability.

The carrier films preferably contain at least one thermoplastic polymer,particularly preferably low-plasticizer or plasticizer-free polyethyleneterephthalate (PET). This is particularly advantageous in terms of thestability of the multilayer film. The carrier films can, however, alsocontain or be made of other low-plasticizer or plasticizer-freepolymers, for example, ethylene vinyl acetate (EVA), polypropylene,polycarbonate, polymethyl methacrylate, polyacrylate, polyvinylchloride, polyacetate resin, casting resins, acrylates, fluorinatedethylene propylenes, polyvinyl fluoride, and/orethylene-tetrafluoroethylene. The thickness of each carrier film ispreferably from 0.04 mm to 1 mm, particularly preferably from 0.05 mm to0.2 mm.

The carrier films have in each case an electrically conductive coatingthat faces the active layer and acts as a surface electrode.

In another advantageous embodiment of a composite pane according to theinvention, the functional element is a PDLC functional element (polymerdispersed liquid crystal). The active layer of a PDLC functional elementcontains liquid crystals that are embedded in a polymer matrix. When novoltage is applied on the surface electrodes, the liquid crystals arerandomly oriented, resulting in strong scattering of the light passingthrough the active layer. The composite pane thus becomes an almosthomogeneous light source. When a voltage is applied on the surfaceelectrodes, the liquid crystals align in a common direction and thetransmittance of light through the active layer is increased. Objectsbehind the pane become visible.

In principle, however, it is also possible to use other types ofcontrollable functional elements, for example, electrochromic functionalelements or SPD functional elements (suspended particle device). Thecontrollable functional elements mentioned and their mode of operationare known per se to the person skilled in the art such that a detaileddescription can be dispensed with here.

Functional elements as multilayer films are commercially available. Thefunctional element to be integrated is typically cut out of a multilayerfilm of relatively large dimensions in the desired shape and size. Thiscan be done mechanically, for example, with a knife. In an advantageousembodiment, the cutting is done using a laser. It has been demonstratedthat, in this case, the side edge is more stable than with mechanicalcutting. With mechanically cut side edges, there can be a risk that acarrier film together with a surface electrode will become detached fromthe functional layer, which is visually conspicuous and adverselyaffects the aesthetics of the pane.

In the composite pane according to the invention, the functional elementis joined to the outer pane via a region of the first intermediate layerand to the inner pane via a region of the second intermediate layer. Theintermediate layers are preferably areally arranged one atop another andlaminated to one another, with the functional element inserted betweenthe two layers. The regions of the intermediate layers overlapping thefunctional element then form the region that joins the functionalelement to the panes. In other regions of the pane where theintermediate layers are in direct contact with one another, they canfuse during lamination such that the two original layers are possibly nolonger discernible and there is, instead, one homogeneous intermediatelayer. A

n intermediate layer can, for example, be formed by a singlethermoplastic film. An intermediate layer can also be formed as atwo-ply, three-ply, or multi-ply film stack, wherein the individualfilms have the same or different properties. An intermediate layer canalso be formed from sections of different thermoplastic films havingadjacent side edges.

In an advantageous development of a composite pane according to theinvention, the region of the first or the second intermediate layer, viawhich the functional element is joined to the outer pane or to the innerpane, is tinted or colored. The transmittance of this region in thevisible spectral range is thus reduced compared to a non-tinted ornon-colored layer. The tinted/colored region of the intermediate layerthus reduces the transmittance of the windshield in the region of thesun visor. In particular, the aesthetic impression of the functionalelement is improved because the tinting results in a more neutralappearance, which has a more pleasant effect on the viewer.

For functional enhancement, an intermediate layer for acousticallyoptimized panes can also consist of three individual plies. In suchcases, the intermediate layer is 0.05 mm to 0.2 mm thicker.

Another alternative is a thermal improvement by means of an IRreflecting coated PET intermediate ply. In this case, the outward-facingintermediate layer also consists of at least three intermediate plies(PVB-PET-PVB). The IR reflecting coating can be directed inward oroutward.

In the context of the invention, “electrically controllable opticalproperties” means properties that are infinitely controllable but alsothose that can be switched between two or more discrete states.

The electrical control of the sun visor is done, for example, usingswitches, rotary knobs, or sliders that are integrated into thedashboard of the vehicle. However, a switch area for controlling the sunvisor can also be integrated into the composite pane to be switched, forexample, a windshield, for example, a capacitive switch area.Alternatively, or additionally, the sun visor can be controlled bycontactless methods, for example, by gesture recognition, or as afunction of the pupil or eyelid state detected by a camera and suitableevaluation electronics. Alternatively, or additionally, the sun visorcan be controlled by sensors that detect light incidence on the pane.

In the transparent state, the tinted or colored region of theintermediate layer preferably has transmittance in the visible spectralrange from 1% to 50%, particularly preferably from 10% to 40%. Withthat, particularly good results are achieved in terms of glareprotection and visual appearance.

The intermediate layer can be formed by a single thermoplastic film,wherein the tinted or colored region is produced by local tinting orcoloring. Such films can be obtained, for example, by coextrusion.Alternatively, a non-tinted film section and a tinted or colored filmsection can be combined to form the thermoplastic layer.

The tinted or colored region can be homogeneously colored or tinted, inother words, can have location-independent transmittance. The tinting orcoloring can, however, be inhomogeneous, in particular a transmittanceprogression can be realized. In one embodiment, the transmittance levelincreases in the tinted or colored region, at least in sections, withincreasing distance from the upper edge. Thus, sharp edges of the tintedor colored area can be avoided such that the transition from the sunvisor into the transparent region of the windshield is gradual,appearing aesthetically more attractive.

In an advantageous embodiment, the region of the first intermediatelayer, i.e., the region between the functional element and the outerpane is tinted. This gives a particularly aesthetic impression when theouter pane is viewed from above. The region of the second intermediatelayer between the functional element and the inner pane can, optionally,be additionally colored or tinted.

In an advantageous embodiment, the inner and/or the outer pane canoptionally be tinted. This results in an optically advantageouscomposite pane. In particular, for vehicle openings in whichtransparency is not limited, such as in the roof area, a visuallyattractive composite pane can be realized.

The composite pane having an electrically controllable functionalelement can advantageously be implemented as a windshield with anelectrically controllable sun visor.

Such a windshield has an upper edge and a lower edge as well as two sideedges extending between the upper edge and the lower edge. “Upper edge”refers to that edge that is intended to point upward in the installationposition. “Lower edge” refers to that edge that is intended to pointdownward in the installation position. The upper edge is often referredto as the “roof edge”; the lower edge, as the “engine edge”.

Windshields have a central field of vision, the optical quality of whichis subject to high requirements. The central field of vision must havehigh light transmittance (typically greater than 70%). Said centralfield of vision is, in particular, that field of vision that is referredto by the person skilled in the art as field of vision B, vision area B,or zone B. The field of vision B and its technical requirements arespecified in Regulation No. 43 of the Economic Commission for Europe ofthe United Nations (UN/ECE) (ECE-R43, “Uniform Provisions concerning theApproval of Safety Glazing Materials and Their Installation onVehicles”). There, the field of vision B is defined in Annex 18.

The functional element is then advantageously arranged above the centralfield of vision (field of vision B). This means that the functionalelement is arranged in the region between the central field of visionand the upper edge of the windshield. The functional element does nothave to cover the entire area, but is positioned completely within thisarea, and does not protrude into the central field of vision. In otherwords, the functional element is less distant from the upper edge of thewindshield than the central field of vision. Thus, the transmittance ofthe central field of vision is not affected by the functional elementwhich is positioned in a location similar to that of a conventionalmechanical sun visor in the folded-down state.

The windshield is preferably provided for a motor vehicle, particularlypreferably for a passenger car.

In a preferred embodiment, the functional element, more precisely theside edges of the functional element are circumferentially surrounded bya third intermediate layer. The third intermediate layer is designedlike a frame with a recess into which the functional element isinserted. The third intermediate layer can also be formed by athermoplastic film into which the recess is introduced by cutting.Alternatively, the third intermediate layer can also be composed of aplurality of film sections around the functional element. Theintermediate layer is preferably formed from a total of at least threethermoplastic layers arranged areally atop one another, wherein themiddle layer has a recess in which the functional element is arranged.During production, the third intermediate layer is arranged between thefirst and the second intermediate layer, with the side edges of allintermediate layers preferably arranged congruently. The thirdintermediate layer preferably has approx. the same thickness as thefunctional element. Thus, the local difference in thickness of thewindshield introduced by the locally limited functional element iscompensated such that glass breakage during lamination can be avoided.

The side edges of the functional element that are visible when lookingthrough the windshield are preferably arranged flush with the thirdintermediate layer such that no gap exists between the side edge of thefunctional element and the associated side edge of intermediate layer.This is in particular true for the lower edge of the functional element,which is typically visible. Thus, the boundary between the thirdintermediate layer and the functional element is visually lessnoticeable.

In a preferred embodiment, the lower edges of the functional element andof the tinted region of the intermediate layer(s) are adapted to theshape of the upper edge of the windshield, yielding a more appealingvisual impression. Since the upper edge of a windshield is typicallycurved, in particular concavely curved, the lower edge of the functionalelement and of the tinted region is also preferably curved. Particularlypreferably, the lower edges of the functional element are substantiallyparallel to the upper edge of the windshield. It is, however, alsopossible to construct the sun visor from two halves, each straight,arranged at an angle relative to one another, and forming a virtuallyV-shaped upper edge.

In one embodiment of the invention, the functional element is dividedinto segments by isolation lines. The isolation lines can, inparticular, be introduced into the surface electrodes such that thesegments of the surface electrode are isolated from one another. Theindividual segments are connected to the voltage source independently ofone another such that they can be actuated separately. Thus, differentregions of the sun visor can be switched independently. Particularlypreferably, the isolation lines and the segments are arrangedhorizontally in the installation position. Thus, the height of the sunvisor can be controlled by the user. The term “horizontal” is to beinterpreted broadly here and refers to a direction of extension that, ina windshield, runs between the side edges of the windshield. Theisolation lines do not necessarily have to be straight, but can also beslightly curved, preferably adapted to possible curvature of the upperedge of the windshield, in particular substantially parallel to theupper edge of the windshield. Vertical isolation lines are, of course,also conceivable.

The isolation lines have, for example, a width of 5 μm to 500 μm, inparticular 20 μm to 200 μm. The width of the segments, i.e., thedistance between adjacent isolation lines can be suitably selected bythe person skilled in the art according to the requirements of theindividual case.

The isolation lines can be introduced by laser ablation, mechanicalcutting, or etching during production of the functional element. Alreadylaminated multilayer films can also be subsequently segmented by laserablation.

The upper edge and the side edges or all side edges of the functionalelement are concealed in vision through the composite pane preferably byan opaque masking print or by an outer frame. Windshields typically havea circumferential peripheral masking print made of an opaque enamel,which serves in particular to visually conceal the adhesive used forinstallation of the window and to protect it against UV radiation. Thisperipheral masking print is preferably used to also conceal the upperedge and the side edge of the functional element as well as thenecessary electrical connections. The sun visor is then advantageouslyintegrated into the appearance of the windshield and only its lower edgeis potentially discernible to the observer. Preferably, both the outerpane and also the inner pane have a masking print such thatthrough-vision is prevented from both sides.

The functional element can also have recesses or holes, for instance, inthe region of so-called sensor windows or camera windows. These regionsare provided to be equipped with sensors or cameras whose function wouldbe impaired by a controllable functional element in the beam path, forexample, rain sensors. It is also possible to realize the sun visor withat least two functional elements separated from one another, with adistance between the functional elements providing space for a sensorwindow or a camera window.

The functional element (or the totality of the functional elements inthe above-described case of a plurality of functional elements) ispreferably arranged over the entire width of the composite pane or ofthe windshield, minus an edge region on both sides having a width of,for example, 2 mm to 50 mm. The functional element also preferably has adistance of, for example, 2 mm to 200 mm from the upper edge. Thefunctional element is thus encapsulated within the intermediate layerand protected against contact with the surrounding atmosphere andcorrosion.

The outer pane and the inner pane are preferably made of glass,particularly preferably of soda lime glass, as is customary for windowpanes. The panes can, however, also be made of other types of glass, forexample, quartz glass, borosilicate glass, or aluminosilicate glass, orrigid clear plastics, for example, polycarbonate or polymethylmethacrylate. The panes can be clear, or also tinted or colored.Windshields must have adequate light transmittance in the central fieldof vision, preferably at least 70% in the primary through-vision zone Aper ECE-R43.

The outer pane, the inner pane, and/or the intermediate layer can havefurther suitable coatings known per se, for example, antireflectioncoatings, nonstick coatings, anti-scratch coatings, photocatalyticcoatings, or solar protection coatings, or low-E coatings.

The thickness of the outer pane and the inner pane can vary widely andthus be adapted to the requirements of the individual case. The outerpane and the inner pane preferably have thicknesses of 0.5 mm to 5 mm,particularly preferably of 1 mm to 3 mm.

The invention also includes a method for producing a functional elementhaving electrically controllable optical properties, wherein at least:

a) a stack sequence formed of a first carrier film, a first surfaceelectrode, an active layer, a second surface electrode, and a secondcarrier film is provided,

b) the first carrier film is cut back at at least one side edge,preferably at all side edges, by a region of the width u, by which meansan overhanging region of the second carrier film is formed, and

c) the overhanging region of the second carrier film is folded aroundthe cut-back side edge of the first carrier film.

In an advantageous embodiment of the method according to the invention,electrical contacting, such as a busbar, is arranged on the overhangingregion of the second carrier film. The electrical contacting can beconnected here to the surface electrode on the second carrier film.

In an advantageous embodiment of the method according to the invention,between steps b) and c), the second surface electrode is removed in theoverhanging region, preferably by mechanical, chemical, and/or physicalremoval, particularly preferably by laser ablation. Alternatively, thesurface electrode can be treated by physical or chemical processes andthus made electrically insulating. All this serves to preventshort-circuits between the first and the second electrode. For complexshapes, additional separating cuts and/or additional material (plastictape) are advantageously introduced.

In an advantageous embodiment of the method according to the invention,at least in one region of another side edge, the second carrier film iscut back, forming an overhanging region of the first carrier film, whichis then folded around the second carrier film. In this region,additional electrical contacting, such as a busbar, can advantageouslybe arranged. The electrical contacting can be connected here to thesurface electrodes on the first carrier film.

Another aspect of the invention also includes a method for producing acomposite pane according to the invention, wherein at least

-   -   a) one outer pane, one first intermediate layer, one functional        element having electrically controllable optical properties, one        second intermediate layer, and one inner pane are arranged one        atop another in this order,    -   b) the outer pane and the inner pane are joined by lamination,        wherein an intermediate layer with an embedded functional        element is formed from the first intermediate layer and the        second intermediate layer.

The electrical contacting of the surface electrodes of the functionalelement is preferably done before the lamination of the composite pane.

Any prints that are present, for example, opaque masking prints orprinted busbars for the electrical contacting contacting of thefunctional element are preferably applied by screen printing.

The lamination is preferably done under the action of heat, vacuum,and/or pressure. Methods known per se can be used for lamination, forexample, autoclave methods, vacuum bag methods, vacuum ring methods,calender methods, vacuum laminators, or combinations thereof.

The invention further includes the use of a composite pane according tothe invention having an electrically controllable functional element asinterior glazing or exterior glazing in a vehicle or a building, whereinthe electrically controllable functional element is used as a sunscreen, as thermal protection, or as a privacy screen.

The invention further includes the use of a composite pane according tothe invention as a windshield or roof panel of a vehicle, wherein theelectrically controllable functional element is used as a sun visor.Here, too, segmentation can be advantageous such that with eliminationof a roller blind or visor, the entry of sun can be individually adaptedlocally.

A major advantage of the invention, in the case of composite panes as awindshield, consists in that a conventional vehicle-roof-mounted,mechanically foldable sun visor can be dispensed with. Consequently, theinvention also includes a vehicle, preferably a motor vehicle, inparticular a passenger car, that has no such conventional sun visor.

The invention also includes the use of a tinted or colored region of anintermediate layer for joining a functional element having electricallycontrollable optical properties with an outer pane or an inner pane ofthe windshield, wherein an electrically controllable sun visor isrealized by means of the tinted or colored region of the intermediatelayer and the functional element. Of course, the tinted or coloredregion can also extend over the entire surface and can include theentire intermediate layer.

The invention is explained in detail with reference to drawings andexemplary embodiments. The drawings are schematic representations andnot true to scale. The drawings in no way restrict the invention. Theydepict:

FIG. 1 an enlarged representation of a detail of a functional elementaccording to the invention,

FIG. 2A a plan view of a composite pane according to the invention,

FIG. 2B a cross-section through the composite pane of FIG. 2A along thesection line X-X′,

FIG. 3A, 3B, 3C, 3D representations of the individual steps forproducing a functional element according to the invention, and

FIG. 4 an exemplary embodiment of the method according to the inventionwith reference to a flowchart.

FIG. 1 depicts an enlarged representation of a detail of a functionalelement 5 according to the invention in the region of a side edge 5.1 ofthe functional element.

The controllable functional element 5 is, for example, a PDLC multilayerfilm comprising an active layer 11 that is arranged between a firstsurface electrode 12 and a second surface electrode 13. The firstsurface electrode 12 has, on the surface facing away from the activelayer 11, a first carrier film 14 that stabilizes the surface electrode12. The second surface electrode 13 has, on the surface facing away fromthe active layer 11, a second carrier film 15 that stabilizes the secondsurface electrode 13. Here, the active layer 11 contains a polymermatrix with liquid crystals dispersed therein, which align themselves asa function of the electrical voltage applied on the surface electrodes12, 13, by which means the optical properties can be controlled. Thecarrier films 14, 15 are made of PET and have a thickness of, forexample, 0.14 mm. The carrier films 14, 15 are provided with a coatingof ITO having a thickness of approx. 100 nm facing the active layer 11,forming the surface electrodes 12, 13. The surface electrodes 12, 13are, for example, applied in a known manner by means of a sputteringprocess. The surface electrodes 12, 13 can be connected to the vehicle'selectrical system via busbars (not shown) (formed by a silver-containingscreen print) and connection cables (not shown).

In the exemplary embodiment depicted, the second carrier film 15 islonger compared to the first carrier film 14; this is also referred toin the following as an overhang or overhanging region 15.1. The secondcarrier film 15 is folded around the first carrier film 14 in theoverhanging region 15.1 at the side edge 5.1. As a result, the exitsurface 20.1 of the active layer 11 is completely covered and sealed atthe side edge 5.1. Here, the exit surface 20.1 identifies the surface ofthe active layer 11 that extends between the first and the secondcarrier films 14, 15 with the first and second surface electrode 12, 13along the side edge 5.1 of the functional element 5 and at which theactive layer 11 routed around has access to the surroundings of thefunctional element 5 without the overhanging region 15.1 of the secondcarrier film 15. The inward surface of the second carrier film 15 isthus arranged on the edge region 14.1 of the outward surface of thefirst carrier film 14. “Inward surface” of the carrier films and“outward surface” of the carrier films refer to the surfaces relative tothe functional element 5.

The width w of the edge region 14.1, i.e., the contact surface of theinward surface of the second carrier film 15 and the outward surface ofthe first carrier film 14 is, for example, 10 mm here and substantiallyextends with a constant width over the entire length of the side edge5.1.

FIG. 2A and FIG. 2B depict in each case a detail of a composite pane 100according to the invention. The composite pane 100 comprises an outerpane 1 and an inner pane 2 that are joined to one another via a firstintermediate layer 3 a and a second intermediate layer 3 b. The outerpane 1 has a thickness of 2.1 mm and is made, for example, of a clearsoda lime glass. The inner pane 2 has a thickness of 1.6 mm and is alsomade, for example, of a clear soda lime glass. The composite pane 100has a first edge referenced with D that is called the “upper edge” inthe following. The composite pane 100 has a second edge referenced withM that is arranged opposite the upper edge D and is called the “loweredge” in the following. The composite pane 100 can be arranged, forexample, as architectural glazing in the frame of a window with otherpanes to form an insulating glazing unit or as a roof panel in the roofof a vehicle. Of course, partition wall panels, side windows, or rearwindows can also be designed advantageously according to the invention.

A functional element 5 according to the invention that is controllablein its optical properties via an electrical voltage is arranged betweenthe first intermediate layer 3 a and the second intermediate layer 3 b.For the sake of simplicity, the electrical leads are not shown.

Here, the functional element according to the invention of FIG. 1 is,for example, the enlarged region Z, which is also reproduced in thefollowing in FIG. 3D.

The intermediate layers 3 a, 3 b include in each case a thermoplasticfilm with a thickness of 0.38 mm. The intermediate layers 3 a, 3 b aremade, for example, of 78 wt.-% polyvinyl butyral (PVB) and 20 wt.-%triethylene glycol bis(2-ethyl hexanoate) as plasticizer.

In this exemplary embodiment, three side edges 5.1, 5.2, 5.3 are sealedaccording to the invention by the folded-around second carrier film 15in each case. The fourth side edge 5.4 is sealed according to theinvention by a folded-around first carrier film 14.

In aging tests, such composite panes 100 present a significantly reducedbrightening in the edge region of the functional element 5, sincediffusion of the plasticizer out of the intermediate layers 3 a, 3 binto the functional element 5 and a resulting degradation of thefunctional element 5 is avoided.

In an advantageous development of the functional element 5 according tothe invention, an adhesive means, for example, an acrylate-basedadhesive, that fixedly glues the carrier films 14, 15 to one another, isarranged between the touching sections of the second carrier film 15 andthe edge region 14.1 of the first carrier film 14. The adhesiveconnection prevents slippage of the carrier films 14, 15 duringassembly. At the same time, inclusions of air bubbles and resultantvisual distractions or impairments are avoided since the folded-aroundsection of the second carrier film 15 rests fixedly on the first carrierfilm 14.

Of course, the composite pane according to the invention is not limitedto the exemplary embodiment presented here. Further exemplaryembodiments not presented here include, for example, windshields or roofpanels of vehicles and the use of electrically controllable functionalelements 5 as sun visors.

FIGS. 3A, 3B, 3C, and 3D depict exemplary embodiments of a functionalelement 5 according to the invention during production.

FIG. 4 depicts an exemplary embodiment of the production methodaccording to the invention with reference to a flowchart with the stepsS1 through S4.

Initially, in a first step S1, a stack sequence formed of a firstcarrier film 14, a first surface electrode 12, an active layer 11, asecond surface electrode 13, and a second carrier film 15 is provided.Such stack sequences are, for example, commercially available by themeter as multilayer film material. Then, the product is customized andtrimmed to the dimensions of the later use, for example, by lasercutting.

FIG. 3A depicts an enlarged representation of the side edge 5.1 of sucha stack sequence in the first step S1. The various elements of the stacksequence, i.e., the first carrier film 14, the first surface electrode12, the active layer 11, the second surface electrode 13, and the secondcarrier film 15 have the same dimensions and are stacked congruentlyatop one another.

In a second step S2, for example, the first carrier film 14 is cut backat at least one side edge and preferably at all side edges of the stacksequence by a region of width u, by means of which an overhanging region15.1 of the second carrier film 15 is formed. The result is accordinglyshown in FIG. 3B for the side edge 5.1. The cut back is done, forexample, by mechanical cutting with a blade along a parallel line at adistance u from the side edge of the first carrier film 14.

In a third step S3, the active layer 11 and the second surface electrode13 are removed in the overhanging region 15.1. The active layer 11 can,for example, be removed by wiping with a cloth and a solvent such aswater or ethanol. The result is accordingly shown in FIG. 3C. Thesurface electrode 13 can, for example, be removed by laser ablation.

In a third step S4, the second carrier film 15 is folded around thecut-back side edge 5.1 of the first carrier film 14 and arranged on theoutward surface of the first carrier film 14 in the edge region 14.1.The result is accordingly shown in FIG. 3D.

The second carrier film 15 can, optionally, be bonded over its entiresurface to the first carrier film 14, for example, by gluing. Thefolded-around carrier film 14 should advantageously contain no adhesivein an edge region, for example, at least in a width w=4 mm, since,otherwise, undesirable edge brightening can occur.

Independently of this, by lamination of the functional element 5according to the invention in a composite pane 100 and by the internalpressure in the finished laminated composite pane 100, the secondcarrier film 15 and the first carrier film 14 are firmly pressed againsteach other in the edge region 14.1 and fixed, resulting in a hermeticseal.

LIST OF REFERENCE CHARACTERS:

1 outer pane

2 inner pane

3 a first intermediate layer

3 b second intermediate layer

5 functional element having electrically controllable optical properties

5.1,5.2,5.3,5.4 side edge of the functional element 5

11 active layer of the functional element 5

12 first surface electrode of the functional element 5

13 second surface electrode of the functional element 5

14 first carrier film

14.1 edge region of the first carrier film

15 second carrier film

15.1 overhanging region of the second carrier film

20.1 exit surface

100 composite pane

D upper edge of the windshield, roof edge

M lower edge of the windshield, engine edge

u overhang, width of the overhanging region 15.1

w width of the edge region 14.1

X-X′ section line

Z enlarged region

1. A functional element having electrically controllable opticalproperties, comprising: a stack sequence formed of a first carrier film,a first surface electrode, an active layer, a second surface electrode,and a second carrier film, wherein the second carrier film is foldedaround the first carrier film at least at one side edge and seals anexit surface of the active layer at the side edge, at least one sectionof an overhanging region is materially bonded to an edge region of thefirst carrier film, is permanently pressed together, is fused, and/or isglued, and the carrier film is implemented such that the carrier filmprevents diffusion of plasticizers through the carrier film.
 2. Thefunctional element according to claim 1, wherein the overhanging regionof the second carrier film has at least a width u of 4 mm.
 3. Thefunctional element according to claim 1, wherein the active layercontains or is made of liquid crystals.
 4. A composite pane having afunctional element having electrically controllable optical properties,comprising: a stack sequence formed of an outer pane, a firstintermediate layer, a second intermediate layer, and an inner pane,wherein the intermediate layers contain at least one thermoplasticpolymer film with at least one plasticizer, and a functional elementhaving electrically controllable optical properties according to claim 1is arranged between the first intermediate layer and the secondintermediate layer at least in sections.
 5. The composite pane accordingto claim 4, wherein the intermediate layer contains at least 3 wt. % ofa plasticizer and the plasticizer contains or is made of aliphaticdiesters of tri-or tetraethylene glycol.
 6. The composite pane accordingto claim 4, wherein the intermediate layer contains at least 60 wt. %polyvinyl butyral (PVB).
 7. The composite pane according to claim 4,wherein the carrier film is implemented such that the carrier filmprevents diffusion of plasticizers through the carrier film.
 8. Thecomposite pane according to claim 4, wherein the carrier film is low inplasticizer or is free of plasticizer.
 9. The composite pane accordingto claim 4, wherein the functional element is circumferentiallysurrounded by a third intermediate layer.
 10. A method for producing afunctional element having electrically controllable optical properties,comprising: a) providing a stack sequence formed of a first carrierfilm, a first surface electrode, an active layer, a second surfaceelectrode, and a second carrier film is provided, b) cutting back thefirst carrier film at at least one side edge by a region of the width u,by which means an overhanging region of the second carrier film isformed, and c) folding the overhanging region of the second carrier filmaround the cut-back side edge of the first carrier film.
 11. The methodaccording to claim 10, wherein, between steps b) and c), the secondsurface electrode is removed in the overhanging region by mechanical,chemical, and/or physical removal.
 12. A method comprising utilizing acomposite pane according to claim 4 as a windshield or roof panel of avehicle and the electrically controllable functional element as a sunvisor.
 13. A method comprising utilizing a composite pane having anelectrically controllable functional element according to claim 1 asinterior glazing or exterior glazing in a vehicle or a building and theelectrically controllable functional element as a sunscreen or as aprivacy screen.
 14. The functional element according to claim 2, whereinthe width u is from 4 mm to 50 mm.
 15. The functional element accordingto claim 3, wherein the active layer is made of polymer dispersed liquidcrystals (PDLC).
 16. The composite pane according to claim 5, whereinthe intermediate layer contains at least 30 wt.-% of a plasticizer. 17.The composite pane according to claim 5, wherein the plasticizer is madeof triethylene glycol bis(2-ethylhexanoate).
 18. The composite paneaccording to claim 6, wherein the intermediate layer contains at least90 wt.-% polyvinyl butyral (PVB).
 19. The composite pane according toclaim 8, wherein the carrier film contains or is made of polyethyleneterephthalate (PET) or polyvinyl fluoride (PVF).
 20. The methodaccording to claim 11, wherein, between steps b) and c), the secondsurface electrode is removed in the overhanging region by laserablation.